<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
    var arr=[1,2,3,4,5]
    var sum=0;
    arr.forEach(function(ele,i,array){
        sum+=ele;
    })
    alert('和是'+sum)
    alert('平均值是'+sum/arr.length)
</script>